Alkylation-transalkylation process



Aug. 10, 1965 c. F. GERALD ALKYLAIION-TRANSALKYLATION PROCESS FiledSept. 8, 1964 INVENTOR Curr/s F. Gerald z zzzp zaw;

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Transa/lry/a/ion Redo/0r m m e w n n yw \lm M Wk \k Km n M o e m NR e0 mu rm m m m w Q 0 m m F m m m H m m M 5km m 4 1 W. A M. V m .v mmm mm m lv .v MW Wm M P mm m 4 K k A TTORA/EYS United States Patent 3,26t),164ALKYLATION-TRANSALKYLATION PROCESS Curtis F. Gerald, an Luis Obispo,Calif., assignor to Universal Uil Products Company, Des Piaines, 121., acorporation of Delaware Filed Sept. 8, 1964, Ser. No. 396,469 19 Claims.(Cl. 260-671) This application is a continuation-in-part of my copendingapplication Serial No. 141,498, filed September 28, 1961, now abandoned.

This invention relates to a process for the production of an aromaticcompound, and more particularly relates to a process for the alkylationof an alkylatable aromatic compound with an olefin-acting compound, andstill more particularly relates to the alkylation of an aromatichydrocarbon with an olefinic hydrocarbon which may be in combinationwith other gases which are unreactive at the process conditionsutilized. Further, this invention .relates to a combination processincluding the steps of alkylation, transalkylation, gas-liquidseparation, fractionation, and gas-liquid absorption.

An object of this invention is to produce alkylated aromatichydrocarbons, and more particularly, to produce monoalkylated benzenehydrocarbons. A specific object of this invention is a process for theproduction of ethylbenzene, a desired chemical intermediate, whichethylbenzene is utilized in large quantities in dehydrogenationprocesses for the manufacture of styrene, one of the starting materialsfor the production of resins and some synthetic rubber. Another specificobject of this invention is to produce alkylated aromatic hydrocarbonsboiling Within the gasoline boiling range having high anti-knock valueand which may be used as such or as a component of gasoline suitable foruse in automobile and airplane engines. A further specific object ofthis invention is a process for the production of cumene by the reactionof benzene with propylene, which cumene prodduct is oxidized in largequantities to form cumene hydroperoxide which is readily decomposed intophenol and acetone. Another object of this invention is to provide aprocess for the introduction of alkyl groups into aromatic hydrocarbonsof high vapor pressure at normal conditions with minimum loss of saidhigh vapor pressure aromatic hydrocarbons and maximum utilizationthereof in the process. Still another object of this invention is aprocess in which molar execesses of aromatic hydrocarbons to bealkylated are utilized, and in which process the yield of monoalkylatedaromatic hydrocarbon product is exceptionally high due to maximumconsumption of polyalkylated aromatic hydrocarbon by-products in theprocess. The further object of maximum boron trifluoride utilization asa catalyst in this process, along with other objects of this invention,will be set forth hereinafter as part of the accompanying specification.

In prior art processes for the alkylation of aromatic hydrocarbons withalkylating agents, it has been disclosed that it is preferable toutilize molar execesses of such aromatic hydrocarbons. In suchprocesess, it is generally preferable to utilize greater than two molsof aromatic hydrocarbon per mol of alkylating agent and in many cases,for best reaction, it is preferred to utilize four or more mols ofaromatic hydrocarbon per mol of alkylating agent. When the alkylatingagent is an olefin hydrocarbon, this has been found to be particularlynecessary to prevent polymerization of the olefin hydrocarbon fromtaking place prior to the reaction of the olefin hydrocarbon with thearomatic hydrocarbon. Further, it has been found advantageous formaximum olefin utilization in the process. Due to the efiect of the Lawof Mass Action, one might expect that the yield of polyalkylatedaromatic hydrocarbons which results therefrom would be minimized. Whilethis is generally true, substantial yields of polyalkylated aromatichydrocarbons are formed even when utilizing such molar excess ofaromatic hydrocarbon reactant. Formation of these polyalkylated aromatichydrocarbons naturally increases the consumption of aromatic hydrocarbonin the process based on the yield of desired alkylated aromatichydrocarbon. This is an obvious economic disadvantage since one seeks toachieve not only maximum alkylating agent consumption in the process,but also, maximum utiliza tion of aromatic hydrocarbon to desiredproduct. The prior art teaches that maximum utilization of aromatichydrocarbon to desired product may be increased by recycling of theby-product polyalkylated aromatic hydrocarbons formed in the processback to the alkylation zone so that simultaneous transalkylation mayoccur. This is to be the usual procedure if the reaction is equilibriumlimited, since equilibrium is achieved by placing all components intoone reactor and then utilizing conditions of temperature, pressure, andresidence time in the reactor to obtain equilibrium. However, it hasbeen found that transalkylation is favored by higher aromatichydrocarbon to alkylating agent ratios than are necessary foralkylation, indicating that kinetics as well as equilibrium must beinvolved in obtaining maximum aromatic hydro carbon utilization. Sincethe higher aromatic hydrocarbon to polyalkylated aromatic hydrocarbonratio favors transalkylation, it would appear to be logical to recyclepolyalkylated aromatic hydrocarbons formed in the process plus recycleand fresh aromatic hydrocarbon to a first transalkylation reactor orzone followed by addition of the alkylating agent to the efliuenttherefrom prior to passage thereof to the alkylation zone. Thisprocedure would insure the highest ratio in the transalkylation zone.Then, this effluent plus alkylating agent could be reacted in analkylation zone at a lower aromatic hydrocarbon to alkylating agentratio since some aromatic hydrocarbon would have been consumed in thetransalkylation zone. However, when attempting to operate in thismanner, the alkylation or second reaction zone catalyst rapid- 1y losesactivity so that unreacted alkylating agent is found in the effluent. Ithas unexpectedly been found that if alkylatable aromatic compound plusolefin-acting compound are reacted in an alkylation zone, andsimultaneously additional alkylatable aromatic compound andpolyalkylated aromatic compound containing substantially nomonoalkylated aromatic compound are reacted in a transalkylation zone,and if the effluents from said reaction zones are flashed by reductionin pressure prior to gas-liquid separation, and the gas-free liquidphases from the alkylation zone and the transalkylation zone arecommingled and then passed to further separation means, the catalyst inboth zones achieves very long life and extremely high conversion of thearomatic compound to monoalkylated derivative thereof is obtained. Thioccurs in spite of the fact that no olefin-acting compound andsubstantially no monoalkylated aromatic compound are present as feed tothe transalkylation zone. In addition, neither inert gas nor ethane ispresent in the transalkylation reaction zone making boron trifluoriderecovery much easier and more efiicient inasmuch as the borontrifluoride becomes part of the flashed liquid aromatic compoundrecycle. By operating according to the process of this invention, avastly superior, improved processing scheme results, and, as compared toprior art processes, not only is this design more economical due tolower heat input requirements, better reaction control and moreeiiicient catalyst utilization, but such an improved processing schemegives great versatility of operation since said processing scheme ismore flexible in an integrated refinery or petrochemical complex thanprevious prior art processes.

A further problem arises in connection With the utilization of molarexcesses of aromatic compound to be alkylated. This problem is relatedto the use of such molar excesses in connection with the alkylation ofaromatic hydrocarbons of high vapor pressure at normal conditions,particularly when the olefin-acting compound utilized is a normallygaseous olefin hydrocarbon such as ethylene, propylene, l-butene,2-butene, or isobutylene, and this problem is further accentuated whenthe alkylation is carried out in the presence of a gaseous acidiccatalyst such as exemplified by boron trifiuoride. The above-mentionedolefin hydrocarbons are often present as minor quantities in variousrefinery gas streams containing major quantities of other gases such ashydrogen, nitrogen, hydrogen sulfide, and hydrocarbons such as methane,ethane, propane, n-butane and isobutane. It has become very desirable toutilize such gas streams for their olefin content and a problem hasarisen therewith which is related thereto and to the utilization of thegaseous acidic catalyst, such as boron trifiuoride. This problem is alsosolved by the utilization of the process of the present invention, whichprocess results in maximum yield of desired alkylated aromatichydrocarbon and minimum loss of alkylating agent, alkylatable aromatichydrocarbon, and gaseous acidic catalyst thereby further yielding aconsiderable economic advantage over prior art processes.

One embodiment of the present invention relates to a process for theproduction of an alkylaromatic compound which comprises alkylating andalkylatable aromatic compound with an olefin-acting compound in thepresence of a catalytic amount of boron trifiuoride in an alkylationreaction zone containing a boron trifiuoridemodified substantiallyanhydrous inorganic oxide, withdrawing and separating from saidalkylation zone a gas phase and a gas-free liquid phase, commingling thegas-free liquid phase from said alkylation zone with a gasfree liquidphase from a transalkylation reaction zone as hereinafter set forth,separating from the resultant gasfree liquid phase mixture unreactedaromatic compound, desired monoalkylated aromatic compound, and highermolecular weight polyalkylated aromatic compound, recycling at least aportion of said unreacted aromatic compound to the alkylation zone,removing desired monoalkylated aromatic compound as product from theprocess, passing said polyalkylated aromatic compound in admixture withalkylatable aromatic compound and boron trifiuoride to a transalkylationzone containing boron trifiuoride-modified substantially anhydrousinorganic oxide and therein reacting the polyalkylated aromatic compoundWith the alkylatable aromatic compound, Withdrawing and separating fromsaid transalkylation zone a gas phase and a gas-free liquid phase, andpassing said gas-free liquid phase to said commingling step asaforesaid.

Another embodiment of the present invention relates to a process for theproduction of an alkylaromatic hydrocarbon which comprises alkylating abenzene hydrocarbon with an olefinic hydrocarbon in the presence of notmore than 1.0 gram of boron trifiuoride per gram mol of olefinichydrocarbon in an alkylation reaction zone containing a borontrifiuoride-modified substantially anhydrous inorganic oxide,withdrawing and separating from said alkylation zone a gas phase and agas-free liquid phase, commingling the gas-free liquid phase from saidalkylation zone with a gas-free liquid phase from a transalkylationreaction zone as hereinafter set forth, separating from the resultantgas-free liquid phase mixture unreacted benzene hydrocarbon, desiredmonoalkylated benzene hydrocarbon, and higher molecular Weightpolyalkylated benzene hydrocarbon, recycling at least a portion of saidunreacted benzene hydrocarbon to the alkylation zone, removing desiredmonoalkylated benzene hydrocarbon as product from the process, passingsaid polyalkylated benzene hydrocarbon in admixture with alkylatablearomatic compound and from 0.002 to about 1.2 grams of boron trifiuorideper gram mol of polyalkylated benzene hydrocarbon to a transalkylationzone containing boron trifiuoride-modified substantially anhydrousinorganic oxide and therein reacting the polyalkylated benzenehydrocarbon with the alkylatable benzene hydrocarbon, withdrawing andseparating from said transalkylation zone a gas phase and a gas-freeliquid phase, and passing said gas-free liquid phase to said comminglingstep as aforesaid.

A further embodiment of the present invention relates to a process forthe production of an alkylaromatic hydrocarbon which comprisesalkylating a benzene hydrocarbon With a normally gaseous olefin in thepresence of not more than 1.0 gram of boron trifiuoride per gram mol ofolefin in an alkylation reaction zone containing a borontrifiuoride-modified substantially anhydrous gamma-alumina, withdrawingand separating from said alkylation zone a gas phase and a gas-freeliquid phase, commingling the gas-free liquid phase from said alkylationzone with a gas-free liquid phase from a transalkylation reaction zoneas hereinafter set forth, separating from the resultant gas-free liquidphase mixture unreacted benzene hydrocarbon, desired monoalkylatedbenzene hydrocarbon and higher molecular weight polyalkylated benzenehydrocarbon, recycling at least a portion of said unreacted benzenehydrocarbon to the alkylation zone, removing desired monoalkylatedbenzene hydrocarbon as product from the process, passing saidpolyalkylated benzene hydrocarbon in admixture with alkylatable benzenehydrocarbon and from about 0.002 to about 1.2 grams of boron trifiuorideper gram mol of polyalkylated benzene hydrocarbon to a transalkylationzone containing boron trifiuoride-modified substantially anhydrousgamma-alumina and therein reacting the polyalkylated benzene hydrocarbonwith the alkylatable benzene hydrocarbon, with drawing and separatingfrom said transalkylation zone a gas phase and a gas-free liquid phase,and passing said gas-free liquid phase to said commingling step .asaforesaid.

A specific embodiment of the present invention relates to a process forthe production of ethylbenzene which comprises alkylating benzene withethylene in the presence of a catalytic amount of boron trifiuoride inan alkylation reaction zone containing a boron trifiuoridemodifiedsubstantially anhydrous alumina, withdrawing and separating from saidalkylation zone a gas phase and a gas-free liquid phase, commingling thegas-free liquid phase from said alkylation zone With a gas-free liquidphase from a transalkylation reaction zone as hereinafter set forth,separating from the resultant gas-free liquid phase mixture unreactedbenzene, desired ethylbenzcne, and high molecular Weightpolyethylbenzenes, recycling at last a portion of said benzene to thealkylation zone, removing desired ethylebenzene as product from theprocess, passing said polyethylbenzenes in admixture with benzene andboron trifiuoride to a transalkylation zone containing borontrifiuoride-modified substantially anhydrous alumina and thereinreacting the polyethylbenzenes with the benzene, withdrawing andseparating from said transalkylation zone a gas phase and a gas-freeliquid phase, and passing said gas-free liquid phase to said comminglingstep as aforesaid.

This invention can be most clearly described and illustrated withreference to the attached drawing. While of necessity, certainlimitations must be present in such a schematic description, nointention is meant thereby to limit the generally broad scope of thisinvention. As stated hereinabove, the first step of the process of thepresent invention comprises alkylating an alkylatable aromatic compoundwith an olefin-acting compound in the presence of a catalytic amount ofboron trifiuoride in an alkylation reaction zone containing a borontrifiuoridemodified substantially anhydrous inorganic oxide. In thedrawing, this first step is represented as taking place in reaction zone9, labeled alkylation reactor. However, the mixture of borontrifluoride, alkylatable aromatic compound, and olefin-acting compoundmust be furnished to this reaction zone. In the drawing, the borontrifiuoride is represented as being furnished to reaction zone 9 throughline 1. The alkylatable aromatic compound, labeled benzene, is combinedtherewith in line 6 by passage through line 2 through pressure controlvalve 3. The olefin-acting compound, labeled ethylene, is combinedtherewith in line 6 by passage through line 4 through pressure controlvalve 5. The combined feed passes to reaction zone 9 via line 8containing heater '7 and is distributed to alkylation zone 9 byconventional distributing means not shown in the drawing but containedin the upper portion of zone 9.

The olefin-acting compound, particularly olefin hydrocarbon, which maybe charged to reaction zone 9 via lines 4 and 8, may be selected fromdiverse materials ineluding monoolefins, diolefins, polyolefins,acetylenic hydrocarbons, and also alcohols, ethers, and esters, thelatter including alkyl halides, alkyl sulfates, alkyl phosphates, andvarious esters of carboxylic acids. The preferred olefin-actingcompounds are olefinic hydrocarbons which comprise monoolefinscontaining one double bond per molecule and polyolefins which containmore than one double bond per molecule. Monoolcfins which are utilizedas olefin-acting compounds in the process of the present invention areeither normally gaseous or normally liquid and include ethylene,propylene, 1-butene, Z butene, isobutylene, and higher molecular weightnormally liquid olefins such as the various pentenes, hexenes, heptenes,octenes, and mixtures thereof, and still higher molecular weight liquidolefins, the latter including various olefin polymers having from about9 to about 18 carbon atoms per molecule including propylene trimer,propylene tetramer, propylene pent-amer, etc. Cycloolefins such asoyclopentene, me-thylcyclopentene, cyclohexene, methylcyclohexene, etc.,may also be utilized. Also included within the scope of theolefin-acting compound are certain substances capable of producingolefinic hydrocarbons or intermediates thereof under the conditions ofoperation utilized in the process. Typical olefin-producing substancesor olefin-acting compounds capable of use include alkyl halides capableof undergoing dehydrohalogenation to form olefinic hydrocarbons and thuscontaining at least two carbon atoms per molecule. Examples of suchalkyl halides include ethyl fluoride, n-propyl fluoride, isopropylfluoride, n-butyl fluoride, isohutyl fluoride, sec-butyl fluoride, tertbutyl fluoride, etc., ethyl chloride, n-propyl chloride, isopropylchloride, nsbutyl chloride, iso butyl chloride, secbutyl chloride,tert-butyl chloride, etc., ethyl bromide, n-propyl bromide, isopropylbromide, n-butyl bromide, isobutyl bromide, sec-butyl bromide,tert-bntyl bromide, etc. As stated hereinabove, other esters such asa-lkyl sulfates including ethyl sulfate, propyl sulfate, etc., and alkylphosphates including ethyl phosphate, etc., may be utilized. Ethers suchas diethyl ether, ethyl propyl ether, dipropyl ether, etc., are alsoincluded Within the generally broad scope of the term olefin-actingcompound and may be successfully utilized as alkylating agents in theprocess of this invention.

Olefin hydrocarbons, particularly normally-gaseous hydrocarbons, areolefin-acting compounds for the use in the process or" this inventionand for passage by means of lines 4 and 8 to reaction zone 9. Theprocess of this invention may be successfully applied to and utilizedfor complete conversion of olefin hydrocarbons when these olefinhydrocarbons are present in minor quantities in various gas streams.Thus, in contrast to prior art processes, the normally gaseous olefinfor use in the process of this invention need not be concentrated. Suchnormally gaseous olefin hydrocarbons appear in minor quantitles invarious refinery gas streams, usually diluted with gases such ashydrogen, nitrogen, methane, ethane, propane, etc. These gas streamscontaining min-or quantities of olefin hydrocarbons are obtained inpetroleum refineries from various refinery installations includingthermal cracking units, catalytic cracking units, thermal reformingunits, coking units, polymerization units, dehydrogenation units, etc.Such refinery gas streams have in the past often been burned for fuelvalue, since an economical process for the utilization of their olefinhydrocarbon content has not been available, or processes which have beensuggested by the prior art utilize such large quantities of alkylatahlearomatic compound that they have not been economically feasible. This isparticularly true for refinery gas streams known as oil-gas streamscontaining relatively minor quantities of olefin hydrocarbons such asethylene. Thus, it has been possible to catalytically polymerizepropylene and/ or butenes in various refinery gas streams, but theoil-gases from such processes still contain the utilizable olefinhydrocarbon, ethylene. In addition to containing ethylene in minorquantities, these ofi-gas streams contain other olefin hydrocarbons,depending upon their source, including propylene and butenes. A refineryoil-gas ethylene stream may contain varying quantities of hydrogen,nitrogen, methane and ethane with the ethylene in minor proportion,while the refinery oil-gas propylene stream is normally diluted withpropane and contains the propylene in minor quantity, and a refineryoff-gas butene stream is normally diluted with butanes and contains thebutenes in minor quantities. A typical analysis in mol percent forutilizable refinery oil-gas from a catalytic cracking unit is asfollows: nitrogen, 4.0%; carbon monoxide, 0.2%; hydrogen, 5.4%; methane,37.8%; ethylene, 10.3%; ethane, 24.7%; propylene, 6.4%; propane, 10.7%and C hydrocarbons, 0.5%. It is readily observed that the total olefincontent of this gas stream is 16.7 mol percent and the ethylene contentis even lower, namely 10.3 percent. Such gas streants containing olefinhydrocarbons in minor or dilute quantities are particularly preferredalkylating agents within the broad scope of this invention. It isreadily apparent that only the olefin content of such streams undergoesreaction at alkylation conditions in the process, and that the remaininggases free from olefin hydrocarbons are vented from the process. It isone of the features of this invention that the gases which do not reactare vented from the process with minimum loss of boron trifiuoride andalkylatable aromatic compounds due to their vapor pressure at theconditions of temperature and pressure utilized for venting thenon-reactive gases.

The olefin-acting compound, acting as the alkylating agent, has combinedtherewith in line 8 alkylatable aromatic compound from line 2 with borontrifiuoride combined therewith from line 1 as will be set forthhereinafter. Many aromatic compounds are utilizable as alkylatablearomatic compounds within the process of this invention. The preferredaromatic compounds are aromatic hydrocarbons, and the preferred aromatichydrocarbons are monocyclic aromatic hydrocarbons, that is, benzenehydrocarbons. Suitable aromatic hydrocarbons include benzene, toluene,ort-ho-Xylene, meta-Xylene, para-Xylene, ethylbenzene,ortho-ethyltolueue, meta-ethyltoluene, paraethyltoluene,1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5 trimethylbenzene,normal propylbenzene, isopropylbenzene or cumene, normal butylbenzene,etc. Higher molecular weight alkylaromatic hydrocarbons are alsosuitable as starting materials and include aromatic hydrocarbons such asare produced by the alkylation of the aromatic hydrocarbons with olefinpolymers. Such products are referred to in the art as alkylate andinclude hexylbenzene, hexyltoluene, nonylbenzene, nonyltoluene,dodecylbenzene, dodecyltoluene, pentadecylbenzene, pentadecyltoluene,etc. Other suitable alkylatable aromatic hydrocarbons include those withtwo or more aryl groups such as diphenyl, diphenylmethane,triphenylmethane, fluorene, stilbene, etc. Examples of alkylatablearomatic hydrocarbons within the scope of this invention utilizable asstarting materials and containing condensed benzene rings includenaphthalene, alpha-methylnaphthalene, beta-methylnaphthalene, etc.,anthracene, phenanthrene, naphthacene, rubrenc, etc. When the selectedalkylated aromatic hydrocarbon is a solid, it may be heated by means notshown so that it passes as a liquid through line 2 or 8 as hereinafterdescribed. Of the alkylatable aromatic hydrocarbons for use as startingmaterials in the process of this invention, the benzene hydrocarbons arepreferred, and of the benzene hydrocarbons, benzene itself isparticularly preferred.

As stated hereinabove, boron trifluoride is added in admixture with thealkylatable aromatic compound prior to passage thereof to line 6. Thisis conveniently accomplished by passage of boron trifluoride from line 1through line 6. Boron trifluoride is a gas, boiling point ll C., meltingpoint l26 C., and is somewhat soluble in most organic solvents. It maybe and generally is utilized per se by mere passage thereof as a gasthrough lines 1 and 6 so that it dissolves at least partially in thealkylatable aromatic compound passing concurrently therewith throughline 6. The boron trifluoride may also be added as a solution of the gasin a suitable organic solvent. However, in the utilization of suchsolutions, care must be exercised so that the selected solvent isunreactive with the alkylating agent or normally gaseous olefinhydrocarbon utilized in the process. Furthermore, boron trifluoridecomplexes with many many organic compounds, particularly thosecontaining sulfur or oxygen atoms. These complexes, while utilizable ascatalysts, are very stable and thus will interfere with the recovery ofboron trifluoride in the gas-liquid absorption zone hereinafter setforth. Therefore, a further limitation upon the selection of such asolvent is that it be free from atoms or groups which from complexeswith boron trifluoride. The amount of boron trifluoride which isutilized is relatively small. It has been found that the amountnecessary can be conveniently expressed as grams of boron trifluorideper gram mol of olefin-acting compound, prefably olefin. This amount ofboron trifluoride will contain not more than 1.0 gram of borontrifluoride per gram mol of olefin utilized. When the amount of borontrifluoride present in the alkylation zone is within the above expressedlimit, substantially complete conversion of the olefin-acting compoundis obtained even when the olefin-acting compound is present in whatmight seem to be minor or dilute quantities in the gas stream.Furthermore, a portion of boron trifluoride then carries over from thealkylation reaction zone to the transalkylation reaction zone ashereinafter described wherein that amount will be utilized again, or incombination with further added boron trifluoride, to cause thetransalkylation reaction to go forward, thus, double use of theoriginally added quantity of boron trifluoride is obtained in thisprocess.

Prior to passage to the alkylation zone, the fresh aromatic compound,olefin-acting compound, and boron tri-fluoride have combined therewithrecycled fractionated unreacted aromatic compound via line 36 andrecycle flashed unreacted aromatic compound containing boron trifluoridevia line 22 as hereinafter set forth. Recycle unreacted aromaticcompound is available in the process since it is preferred to utilize amolar excess of alkylatable aromatic compound over olefin-actingcompound, preferably olefin. This, as is disclosed in the prior art, hasbeen found necessary to prevent side reactions from taking place suchas, for example, polymerization of the olefin-acting compound prior toreaction thereof with the alkylatable aromatic compound and to directthe reaction principally to monoalkylation. Any molar excess ofalkylatable aromatic compound may be utilized, although best results areobtained when the alkylatable aromatic compound to olefin-actingcompound molar ratio is from about 4:1 to about :1 or more.

The combined feed to the alkylation reaction zone comprising alkylatablearomatic compound in a molar excess based on the alkylating agent, andboron trifluoride provided in a manner hereinabove specified is passedto reactor 9 containing the alkylation zone. Reactor 9 is of theconventional type with a boron trifluoride-modified inorganic oxidedisposed therein in the reaction zone. In addition, the reactor may beequipped with heat transfer means, bafiies, trays, heating means, etc.The reactor is preferably of the adiabatic type and thus the feed to thereactor will preferably be provided with the requisite amount of heatprior to passage thereof to said reactor. As set forth hereinabove, thealkylation reaction zone is packed with a boron trifluoride-modifiedinorganic oxide. The inorganic oxide with which the zone in the reactoris packed may be selected from among diverse inorganic oxides includingalumina, silica, boria, oxides of phosphorus, titanium dioxide,zirconium dioxide, chromia, zinc oxide, magnesia, calcium oxide,silica-alumina, silica-magnesia, silica-alumina-magnesia,silica-alumina-zirconia, chromia-alumina, alumina-boria,silica-zirconia, etc., and various naturally occurring inorganic oxidesof various states of purity such as bauxite, clay (which may or may nothave been previously acid treated), diatomaceous earth, etc. Of theabove-mentioned inorganic oxides, gamma-alumina and theta-alumina aremost readily modified by boron trifluoride, and thus the use of one orboth of these boron trifluoride-modified aluminas is preferred. Themodification of the inorganic oxide, particularly alumina, may becarried out prior to or simultaneous with the passage of the reactantscontaining boron trifluoride to the reactor. The exact manner in whichthe inorganic oxides are modified by boron trifluoride is not completelyunderstood. However, it has been found that the modification ispreferably carried out at a temperature at least as high as thatselected for use in the particular zone, so that the catalyst in saidzone will not exhibit an activity induction period. If the inoragnicoxide is modified prior to use, this modification may be carried out insitu in the reactor or in a separate catalyst preparation step. Moresimply, this modification is accomplished by mere passage of borontrifluoride gas over a bed of the inorganic oxide maintained at thedesired temperature. If the modification of the inorganic oxide withboron trifluoride is carried out during the passage of the reactantsthereover, the catalyst will exhibit an induction period and thuscomplete reaction of the alkylating agent with the alkylatable aromaticcompound, and transalkylation of the recycled polyalkylated aromaticcompounds will not take place for some hours, say up to 12 or more.

The conditions utilized in reaction zone 0 may be varied over arelatively wide range. Thus, the desired alkylation reaction in thepresence of the above indicated catalyst may be effected at atemperature of from about 0 or lower to about 250 C. or higher. Thealkylation reaction is usually carried out at a pressure of from aboutsubstantially atmospheric, preferably from about 15 to about 200atmospheres or more. The pressure utilized is usually selected tomaintain the alkylatable aromatic compound in substantially liquid phasewhich is readily accomplished when utilizing relatively pure,concentrated components. However, within the above-mentioned temperatureand pressure ranges, it is not always possible to maintain theolefin-acting compound in completely liquid phase. Thus, when utilizinga refinery off-gas containing ethylene as the olefin-acting compound,the dilute ethylene stream will be dissolved in the liquid phasealkylatable aromatic compound (and alkylated aromatic compound asformed) to the extent governed by temperature, pressure, and solubilityconsiderations. However, a small portion thereof will always be in thevapor phase. The hourly liquid space velocity of the liquid through thealkylation zone may be varied over relatively wide range of from about0.1 to about 20 or more.

When the alkylation reaction has proceeded to the desired extent,preferably with 100% conversion of the olefin-acting compound, theproducts from the allrylation zone which may be termed alkylation zoneeflluent, pass from allrylation reaction zone 9 via line It) throughpressure control valve 11 to line 12, where the eflluent is cooled andcondensed in condenser 13 from which the gases and liquids pass to flashdrum 14-. Pressure control valve 11 generally is set so that asubstantial pressure drop, preferably of about 200 p.s.i.g., occurs fromline 16 to line 12. This accomplishes the purpose of allowingcondensation of the heavier components of the effluent while stillallowing a flashing of the gases and a portion of the alkylatablearomatic compound from flash drum 14 through line 15. In line 15 thereis another cooler or condenser 16 which is maintained at a lowertemperature than condenser 13 and further accomplishes the condensationof un'condensed alkylatable. aromatic compound which passes through line15 along with the gases from flash drum 14. By the utilization of thelow pressure flash drum separation, all of the products in the effluentwhich are gaseous at atmospheric conditions can be separated inseparator 17 and passed therefrom through line 18 to countercurrentgas-liquid absorber 19, hereinafter described. The condensable materialsin separator 17, comprising mainly alkylatable aromatic compounds arewithdrawn therefrom from line 20 by pump 21 which passes the same vialine 22 for recycle to the alkylation zone. The flash drum also freesthe liquid etlluent there in from gaseous components in the eflluent andthus a gas-free liquid phase is Withdrawn from flash drum 14 throughline 23 by pump 24 which passes the same via line 25 to a comminglingstep. The thereinabove mentioned gas-free liquid phase is then passedfrom the commingling step, hereinafter described, though line 26 tofractionation zone 27, labeled benzene column.

Fractionation zone 2'7 is a conventional fractionator distillationcolumn or tower and utilized for the purpose of recovering excessunreacted alkylatable aromatic compound from the alkylation reactionzone effluents for recycle. The recovered unreacted alkylatable aromaticcompound passes overhead from fractionation zone 27 through line 23containing condenser 29 to overhead receiver St The unreactedalirylatable aromatic compound recovered overhead from fractionationzone 27 is withdrawn from overhead receiver 3% through line 31 by pump32 which provides reflux to fractionation zone 27 by means of lines 33and 34 and which also recycles the remainder or net amount of therecovered alkylatable aromatic compound via lines 33 and 35 to line 36which recycles the same to the alkylation reaction zone 9. The higherboiling alkylated aromatic compounds are withdrawn from fractionationzone 27 through line it? and passed to fractionation zone 41, labeledethylbenzene column. The requisite amount of heat is furnished tofractionation zone 27 by reboiler 39 whic heats and recycles a portionof the high boiling allrylated aromatic compounds back to fractionationzone 27 through line 38.

Second fractionation zone 41 is of the conventional type and is utilizedfor recovering of desired alkylated aromatic compound from higherboiling homologs there of. The desired alkylated aromatic compound isWithdrawn overhead from fractionation zone 41 through line 42 containingcondenser 43 and is passed to overhead receiver 44. The liquid productfrom overhead receiver 44 comprises desired alkylated aromatic compoundwhich is withdrawn therefrom through line 45 by pump 46 which providesreflux to fractionation zone 41 by means of lines 47 and 43. Pump 46also provides a means for passage of the desired alkylated aromaticcompound from the process by means of line 49, labeled product tostorage. The still higher boiling polyalkylated aromatic compounds arewithdrawn from fractionation zone 41 by means of line 52. The requisiteamount of heat is provided to fractionation zone 41 by reboiler 51through id which a portion of the higher boiling polyalkylated aromaticcompounds is passed by means of line 5d.

The higher boiling polyallrylated aromatic compounds may be passeddirectly from fractionation zone 41 for use as absorber oil ingas-liquid absorption zone 19, or they may be passed to furtherfractionation as hereinafter described. When direct passage of thesehigher boiling polyalltylated aromatic compounds to the absorption zoneis desired, control valve 58 is opened and control valve 54 is closed.The higher boiling polyalkylated aromatic compounds pass fromfractionation zone 41 via lines 52 and 57 through control valve 58through line 5 into an upper region of gas-liquid absorption zone 19.

Absorption zone 19, labeled absorber, is a countercurrent contactingzone, of conventional design, the size of which is varied depending uponthe quantity of polyalkylated aromatic compounds passed thereto and uponthe quantity of unreacted aromatic compound, boron trifluoride, andunreacted gases passed to a lower region thereof. In gas-liquid absorber1.9, the higher boiling polyalkylated aromatic compounds flowing throughline 59 flow downward in a countercurrent manner to the ascending gaseswhich are introduced thereto in a lower region thereof, for example, vialine 18. The unreactive gases are vented from absorption zone 19 throughline til containing valve (Ed. The polyalkylated aromatic compound andat least a portion of the boron trifluoride and any alkylatable aromaticcompound which may have been passed thereto from separator 17 arewithdrawn from the bottom of absorption zone 19 through line 62 andpassed to transalkylation zone 81 via lines 63 and 96 as hereinafterdescribed.

When direct passage of these higher boiling polyalkylated aromaticcompounds to the next fractionation zone is desired, pressure controlvalve 53 is closed and pressure control valve 54 is opened. The higherboiling polyalkylated aromatic compounds pass from fractionation zone 41via lines 52 and 53 through pressure control valve 54 through line 55 tofractionation zone 56, labeled polyethylbenzene column. Fractionationzone 56 is of the conventional type and the polyalkylated aromaticcompounds are fractionated therein to remove the desired recycle asoverhead therefrom. The desired polyalkylated aromatic compound recyclepasses overhead from column 65 through line 64 containing condenser 65to overhead receiver 66. The liquid is withdrawn from overhead receiver66 through line 67 by pump 63 which provides reflux for fractionationzone 56 by means of lines 69 and 7d. The net amount of polyalkylatedaromatic compound is passed by pump 68 through line 6% and "731 throughpressure control valve 72 to line 76 and then to transalkylation zone 81are hereinafter described. The column is supplied with the necessaryamount of heat by reboiler '74 which recycles a portion of the higherboiling bottoms back to the column through line 73. A portion of thehigher boiling bottoms may be withdrawn through line '75.

The polyalkylated aromatic compound from overhead receiver as, ashereinbefore described, is passed to transalkylation zone 81 via line76. However, prior to passage of the polyalkylated aromatic compound totransalkylation zone 81, these compounds have combined therewithunreacted fractionated alkylatable aromatic compound via lines 37 and63, and with unreacted flashed alkylatable aromatic compound via linesand 96 as hereinafter described to provide a molar excess thereof inrelation to the allryl groups contained in the polyalkylated aromaticcompounds passed to said transalkylation zone. Furthermore, a quantityof boron trifluoride in the amount of 0.002 gram to about 1.2 grams ofboron trifluoride per gram mol of polyalkylated aromatic compound isadded to the transalkylation zone via lines 62 and 63 from gas-liquidabsorption zone 19 as hereinbefore described as well as from line 95. Ifnecessary, and/ or desirable an additional amount of boron trifluoridemay be added through line 77 containing pressure control valve 78 vialine 76. Thus, a transalkylation reaction zone combined feed ofpolyalkylated aromatic compounds, alkylatable aromatic compound andboron trifluoride passes through mixing line 76 through heater '79 vialine to transalkylation reaction zone Transalkylation reaction zone 31is of the conventional type and may be equipped with heat transfermeans, baffles, trays, heating means, etc. The reactor is preferably ofthe adiabatic type and thus the feed to the reactor will preferably beprovided with the requisite amount of heat prior to passage thereof tosaid reactor. As set forth hereinabove, the reaction zone is packed witha boron trifluoride-modified inorganic oxide. The particular borontrifluoride-modified inorganic oxide is generally selected so that thesame material is utilized in both the alkylation reaction zone and thetransalkylation reaction zone. Since the conditions necessary fortransalkylation are generally more severe than for alkylation, oneeffective means for increasing severity is by utilization of a bed ofboron trifluoride-rnodified inorganic oxide in transalkylation zone 81of greater depth than was utilized as in the alkylation zone 9. By theutilization of such greater bed depth, one effectively decreases theliquid hourly space velocity of the combined feed therethrough and thusincreases reaction zone severity. As was the case with the conditionsutilized in the alkylation reaction zone, the conditions utilized intransalkylation reaction zone 81 may be varied over a relatively widerange, but, as set forth hereinabove, are usually of greater severitythan prevail in the alkylation reaction zone. Various means other thanincreasing catalyst bed depth and decreasing liquid hourly spacevelocity may be utilized for increasing this reaction zone severity. Forexample, the mol concentration of boron trifluoride in transalkylationzone 81 may be greater than for alkylation zone 9 by passage ofadditional boron trifiuoride thereto via line 77. Also, when thealkylation reaction zone and transalkylation reaction zone are separatedas shown in the drawing, one may effectively increase the temperature byproper placement of heating means before each reactor. Thetransalkylation reaction may be effected at temperatures of from aboutto about 300 C. or higher and at a pressure of from about substantiallyatmospheric, preferably from about 15 to about 200 atmospheres. Thepressure utilized is selected to maintain the alkylatable aromaticcompound and polyalkylated aromatic compounds in liquid phase. Referringto the alkylatable aromatic compound, it is preferable to have presentin the transalkylation reaction zone from about 1 to about 10 or more,sometimes up to 20, molar proportions per molar proportion of alkylgroup in the polyalkylated aromatic hydrocarbon introduced therewith.The hourly liquid space velocity of the liquid through transalkylationreaction zone 81 may be varied over a relatively wide range of fromabout 0.1 to about 20 or more. It is a feature of the present inventionthat the alkylatable aromatic compound to polyalkylated aromaticcompound ratio in the transalkylation reaction zone can be varied independently of the alkylation reactor rates. When the transalkylationreaction has proceeded to the desired extent so that a sufficientquantity of polyalkylated aromatic compounds are converted tomonoalkylated aromatic compounds by reaction with alkylatable aromaticcompound, the products from transalkylation zone 81 are withdrawnthrough line 82 for recovery of the desired components therefrom.

The transalkylation reaction zone efliuent passes through line 82through line 84 containing pressure control valve 83 where the efiiuentis cooled and condensed in condenser 85 from which the gases and liquidspass to flash drum 86. Pressure control valve 83 generally is set sothat a substantial pressure drop, preferably of about 200 p.s.i.g.,occurs from line 82 to line 84. This accomplishes the purpose ofallowing condensation of the heavier components of the effluent whilestill allowing the flashing of the gases and a portion of thealkylatable aromatic compound from flash drum through line 87. In line87, there is another cooler or condenser 83 which is maintained at alower temperature than condenser 85 and further accomplishes thecondensation of uncondensed alkylatable aromatic compound which passesthrough line 87 along with the gases from flash drum 86. The flash drumalso frees the liquid efiiuent therein from gaseous components in theeffluent and thus a gas-free liquid phase is withdrawn from flash drum86 through line so by pump 91 which passes the same via line 92 to acommingling step as hereinbefore mentioned.

By the utilization of the low-pressure flash drum separation, thecondensible materials in separator 89, comprising mainly alkylatablearomatic compound in admixture with boron trifiuoride, are withdrawntherefrom via line 93 by pump 94 to line 95 for recycle to thetransalkylation reaction zone via line 96 as hereinabove set forth.

The commingling step comprises withdrawing the gasfree liquid phase fromalkylation reaction zone flash drum 14 via line 25 and Withdrawing thegas-free liquid phase from transalkylation reaction zone flash drum 86via line 92 and passing the resultant gas-free liquid phase mixture vialine 26 to fractionation zone 27. By the utilization of the comminglingstep, the unreacted aromatic compound, monoalkylated aromatic compound,and polyalkylated aromatic compounds are fed directly to thefractionators for separation into the desired components as hereinabovedescribed. The following example is introduced for the purpose ofillustration with no intention of unduly limiting the generally broadscope of the present invention. This example is carried out in a benchscale pilot plant equipped with two separate reactors, gas-liquidseparation means, fractionation means for separation and recycle ofexcess alkylatable aromatic compound, fractionation means for separationand recovery of monoalkylated aromatic compound, and recycle means forpolyalkylated aromatic compound. The reactors are equipped with separateheating means so that the temperature in each can be maintained atditferent levels. The alkylation reactor is of suflicient size so that abed of approximately cc. of boron trifluoride-modified gamma-aluminacould be utilized therein. The transalkylation reactor is of sufficientsize so that a bed of approximately 200 cc. of borontrifluoride-modified gamma-alumina could be utilized therein.

The boron trifluoride-modified gamma-alumina utilized is prepared bytreating gammaalumina with a mixture of boron trifiuoride and nitrogenat a temperature of approximately 300 F. After loading the thus modifiedalumina into the separate reactors, its temperature is raised to 300 C.and it is again treated with 22% boron trifluoride and nitrogen toinsure modification thereof. The feed stocks utilized consisted ofbenzene, a synthetic off-gas consisting of about 11% ethylene innitrogen, and polyethylated benzene hydrocarbons produced in theprocess.

This example illustrates the process of the present invention for theproduction of ethylbenzene utilizing the flow scheme as shown in thedrawing. In this example, benzene and ethylene are fed to the alkylationreaction zone containing a boron trifluoride-modified substantiallyanhydrous gamma-alumina along with a catalytic amount of borontrifluoride. The gas-free liquid phase that is withdrawn and separatedfrom the alkylation zone is commingled with the gas-free liquid phasethat is withdrawn and separated from the transalkylation zone and fromthe commingling step, unreacted benzene, desired ethylbenzene, andhigher molecular weight polyethylbenzenes are separated. A portion ofthe unreacted benzene is recycled to the alkylation zone, and thedesired ethylbenzene is removed as product from the process.

The polyethylbenzenes are passed in admixtures With unreacted benzeneand boron trifluoride to the transalkylation reaction zone alsocontaining a boron trifluoridemodified substantially anhydrousgamrna-alumina and therein reacts the polyethylbenzenes with thebenzene, and .a gas-free liquid phase is withdrawn and separated fromthe transalkylation zone and recycled to the commingling step ashereinabove set forth.

The test is carried out at pressure of 530 p.s.ig. for both reactorswith a maximum temperature of 235 C. in the alkylation reaction zone anda maximum temperature of 258 C. in the transalkylation reaction zone. Inthe test, 525 cc. per hour of benzene and 28.0 grams per hour ofethylene in the form of a synthetic off-gas is passed to the alkylationreactor. Along with this feed, there is also passed to this reactor 0.05gram per hour of boron trifluoride. The benzene to olefin mol ratio inthe alkylation reactor is kept at about 6:1. The effluent from thealkylation reactor is flashed by a reduction in pressure prior togas-liquid separation, and a total of 223 grams of unreacted benzene isrecycled back to the reactor while a total of 180 grams of unreatcedbenzene, ethylbenzene, and polyethylbenzenes pass to the fractionationzones for separation into the desired components. All of the gaseousproducts are passed to the absorber where the polyethylbenzenes and theboron trifluoride and any unreacted benzene passed thereto is passed tothe transalkylation zone. A' total of approximately 125 cc. of benzeneand 25 grams of polyethylbenzenes is passed to the transalkylationreaction zone so that a benzene to ethyl group ratio of about 2 ismaintained. In addition, there is added an additional amount of borontrifluoride so that the total quantity of boron trifluoride passing tothe transalkylation reaction zone is maintained at approximately 0.20gram per hour. The eiiluent from the transalkylation reaction zone isflashed by a reduction in pressure prior to gas-liquid separation and atotal of 85 grams of the gas-free liquid phase is passed to-thecommingling step where the gasfree liquid phases from both reactors joinand then pass as a gas-free liquid phase mixture to the fractionationzones for separation into the desired components.

In this twenty-four hour test period illustrating the process of thepresent invention, ethylene conversion starts out at 100% and continuesat 100% throughout the entire test. During the test, completetransalkylation of the polyethylbenzenes continues so that ethylbenzenesyields based on benzene reacted approach the stoichiometric yields andcontinue at this high level. Simultaneously, no catalyst deactivation isobserved for the entire test period.

I claim as my invention:

1. A. process for the production of an alkylaromatic compound whichcomprises alklating an alkylatable aromatic compound with anolefin-acting compound in the presence of a catalytic amount of borontrifluoride in an alkylation reaction zone containing a borontrifluoride'modified substantially anhydrous inorganic oxide, flashingthe efiduent from said alkylation zone by pressure reduction and thenseparating the same into a gas phase and a gas-free liquid phase,commingling said gas-free liquid phase with a gas-free liquid phase froma transalkylation zone as hereinafter set forth, fractionating theresultant gas-free liquid phase mixture and separating therefromunreacted aromatic compound, desired monoalkylated aromatic compound,and higher molecular weight polyalkylated aromatic compound, recyclingat least a portion of said unreacted aromatic compound to the alkylationzone, removing desired monoalkylated aromatic compound as product fromthe process, passing said polyalkylated aromatic compound in admixturewith alkylatable aromatic compound and boron trifluoride to atransalkylation zone containing boron trifluoride-modified substantiallyanhydrous inorganic oxide and therein reacting the polyalkylatedaromatic compound with the alkylatable aromatic compound, flashing theeiliuent from said transalkylation zone by pressure reduction and thenseparating the same into a gas phase and a gas-free liquid phase, andpassing the last-named gas-free liquid phase to said commingling step asaforesaid.

2. The process of claim 1 further characterized in that said alkylatablearomatic compound is an alkylatable aromatic hydrocarbon.

3. The process of claim 1 further characterized in that said alkylatablearomatic compound is a benzene hydrocarbon.

4. The process of claim 3 further characterized in that saidtransalkylation reaction zone contains from about 0.0002 to about 1.2grams of boron trifluoride per gram mol of polyalkylated aromaticcompound and in that said alkylation reaction zone contains not morethan 1.0 gram of boron trifluoride per gram mol of olefin-actingcompound.

5. The process of claim 4 further characterized in that saidolefin-acting compound is an olefinic hydrocarbon.

6. The process of claim 4 further characterized in that saidolefin-acting compound is a normally gaseous olefin.

7. The process of claim 6 further characterized in that said inorganicoxide is a substantially anhydrous alumina.

8. The process of claim 6 further characterized in that saidsubstantially anhydrous inorganic oxide is gamma-alumina.

9. The process of claim 6 further characterized in that saidsubstantially anhydrous inorganic oxide is thetaalumina.

10. A process for the production of ethylbenzene which comprisesalkylating benzene with ethylene in the presence of a catalytic amountof boron trifluoride in an alkylation reaction zone containing a borontrifluoride-modified substantially anhydrous alumina, flashing theefiluent from said alkylation zone by pressure reduction and thenseparating the same into a gas phase and a gas-free liquid phase,commingling said gas-free liquid phase with a gas-free liquid phase froma transalkylation reaction zone as hereinafter set forth, fractionatingthe resultant gas-free phase mixture and sepa rating therefrom unreactedbenzene, desired ethylbenzene, and higher molecular weightpolyethylbenzenes, recycling at least a portion of said unreactedbenzene to the alkylation zone, removing desired ethylbenzene as productfrom the process, passing said polyethylbenzenes in admixture withbenzene and boron trifluoride to a transalkylation zone containing borontrifluoride-modified substantially anhydrous alumina and thereinreacting the polyethylbenzenes with the benzene, flashing the effiuentfrom said transalkylation zone by pressure reduction and then separatingthe same into a gas phase and a gas-free liquid phase, and passing thelast-named gasfree liquid phase to said commingling step as aforesaid.

11. A process for the production of cumene which comprises alkylatingbenzene with propylene in the presence of a catalytic amount of borontrifluoride in an alkylation reaction zone containing a borontrifluoridemodiiied substantially anhydrous gamma-alumina, flashing theefliuent from said alkylation zone by pressure reduction and thenseparating the same into a gas phase and a gas-free liquid phase,commingling said ga'sfree liquid phase with a gas-free liquid phase froma transalkylation reaction zone as hereinafter set forth, fractionatingthe resultant gas-free liquid phase mixture and separating therefromunreacted benzene, desired cumene, and higher molecular weightpolypropylbenzenes, recycling at least a portion of said unreactedbenzene to the alkylation zone, removing desired cumene as product fromthe process, passing said polypropylbenzenes in admixture with benzeneand boron trifluoride to a transalkylation zone containing borontrifluoride-modified substantially anhydrous gamma-alumina and thereinreacting the polypropylbenzenes With the benzene, flashing theeflluent 1. 5 from said transalkylation zone by pressure reduction andthen separating the same into a gas phase and a gas-free liquid phase,and passing the last-named gas-free liquid phase to said comminglingstep as aforesaid.

12. A process for the production of butylbenzene which comprisesalkylating benzene with a butene in the presence of a catalytic amountof boron trifluoride in an alkylation reaction zone containing a borontrifluoride-modified substantially anhydrous alumina, flashing theeflluent from said alkylation zone by pressure reduction and thenseparating the same into a gas phase and a gas-free liquid phase,commingling said gas-free liquid phase with a gas-free liquid phase froma transalkylation reaction zone as hereinafter set forth, fractionatingthe resultant gas-free liquid phase mixture and separating therefromunreacted benzene, desired butylbenzene, and higher molecular Weightpolybutylbenzenes, recycling at least a portion of said unreactedbenzene to the alkylation zone, removing desired butylbenzene as productfrom the process, passing said polybutylbenzenes in admixture withbenzene and boron trifluoride to a transalkylation zone containing borontrifluoride-modified substantially anhydrous alumina and thereinreacting the polybutylbenzenes with the benzene, flashing the effluentfrom said transalkylation zone by pressure reduction and then separatingthe same into a gas phase and a gas-free liquid phase, and passing thelast-named gas-free liquid phase to said commingling step as aforesaid.

13. A process for the production of ethylbenzene which comprisesalkylating benzene with a refinery offgas containing a minor quantity ofethylene in the presence of a catalytic amount of boron trifluoride inan alkylation reaction zone containing a boron trifluoridemodifiedsubstantially anhydrous alumina, flashing the efliuent from saidalkylation zone by pressure reduction and then separating the same intoa gas phase and a gasfree liquid phase, commingling said gas-free liquidphase with a gas-free liquid phase from a transalkylation reaction zoneas hereinafter set forth fractionating the resultant gas-free liquidphase mixture and separating therefrom unreacted benzene, desiredethylbenzene, and higher molecular weight polyethylbenzenes, recyclingat least a portion of said unreacted benzene to the alkylation zone,

16 removing desired ethylbenzene as product from the process, passingsaid polyethylbenzenes in admixture with benzene and boron trifluorideto a transalkylation zone containing boron trifiuoride-modifiedsubstantially anhydrous alumina and therein reacting thepolyethylbenzenes with the benzene, flashing the effluent from saidtransalkylation zone by pressure reduction and then separating the sameinto a gas phase and a gas-free liquid phase, and passing the last-namedgas-free liquid phase to said commingling step as aforesaid.

14. The process of claim 1 further characterized in that the alkylationconditions are a temperature of from about 0 to about 250 C., a pressureof from about atmospheric to about 200 atmospheres, and a liquid hourlyspace velocity of from about 0.1 to about 20.

15. The process of claim 1 further characterized in that thetransalkylation conditions are a temperature of from about 50 to 300 C.,a pressure of from about atmospheric to about 200 atmospheres, and aliquid hourly space velocity of from about 0.1 to about 20.

16. The process of claim 1 further characterized in that the alkylationand transalkylation zones are confined within separate reaction vessels.

17. The process of claim 1 further characterized in that the quantity ofboron trifiuoride present in the alkylation zone is less than thatpresent in the transalkylation zone.

13. The process of claim 1 further characterized in that the borontrifiuoride furnished to the transalkylation zone is supplied solelyfrom the alkylation zone.

19. The process of claim 1 further characterized in that both thealkylation zone and transalkylation zone effluents are flashed by areduction in pressure of about 200 pounds per square inch.

References Cited by the Examiner UNITED STATES PATENTS 2,373,062 4/45Stahly 260-672 2,756,261 7/56 Fetterly 260672 2,995,611 8/61 Linn et al260-672 PAUL M. COUGHLAN, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

1. A PROCESS FOR THE PRODUCTION OF AN ALKYLAROMATIC COMPOUND WHICHCOMPRISES ALKYLATING AN ALKYLATABLE AROMATIC COMPOUND WITH ANOLEFIN-ACTING COMPOUND IN THE PRESENCE OF A CATALYTIC AMOUNT OF BORONTRIFLUORIDE IN AN ALKYLATION REACTION ZONE CONTAINING A BORONTRIFLUORIDE-MODIFIED SUBSTANTIALLY ANHYDROUS INORGANIC OXIDE, FLASHINGTHE EFFLUENT FROM SAID ALKYLATION ZONE BY PRESSURE REDUCTION AND THENSEPARATING THE SAME INTO A GAS PHASE AND A GAS-FREE LIQUID PHASE,COMMINGLING SAID GAS-FREE LIQUID PHASE WITH A GAS-FREE LIQUID PHASE FROMA TRANSALKYLATION ZONE AS HEREINAFTER SET FORTH, FRACTIONATING THERESULTANT GAS-FREE LIQUID PHASE MIXTURE AND SEPARATING THERFROMUNREACTED AROMATIC COMPOUND, DESIRED MONALKYLATED AROMATIC COMPOUND, ANDHIGHER MOLECULAR WEIGHT POLYALKYLATED AROMATIC COMPOUND, RECYCLING ATLEAST A PORTION OF SAID UNREACTED AROMATIC COMPOUND TO THE ALKYLATIONZONE, REMOVING DESIRED MONALKYLATED AROMATIC COMPOUND AS PRODUCT FROMTHE PROCESS, PASSING SAID POLYALKYLATED AROMATIC COMPOUND IN ADMIXTUREWITH ALKYLATABLE AROMATIC COMPOUND AND BORON TRIFLUORIDE TO ATRANSALKYLATION ZONE CONTAINING BORON TRIFLURODIE-MODIFIED SUBSTANTIALLYANHYDROUS INORGANIC OXIDE AND THEREIN REACTING THE POLALKYLATED AROMATICCOMPOUND WITH THE ALKYLATABLE AROMATIC COMPOUND, FLASHING THE EFFLUENTFROM SAID TRANSALKYLATION ZONE BY PRESSURE REDUCTION AND THEN SEPARATINGTHE SAME INTO A GAS PHASE AND A GAS-FREE LIQUID PHASE, AND PASSING THELAST-NAMED GAS-FREE LIQUID PHASE TO SAID COMMINGLING STEP AS AFORESAID.